The alphavirus Sindbis will serve as a model for studies on the processes involved in the assembly of enveloped viruses. Information will be gathered on the processing of virus membrane proteins and the interactions of virus proteins with other virus proteins and host components as the virus proteins are moved from their sight of synthesis to the cell surface. The final stages in the envelopment of the virus will be studied to determine the topological arrangement of precursors to the virus envelope glycoproteins in the infected cell plasma membrane and the reorganization of these virus proteins as building of the virion takes place. Sindbis virus capsid protein-RNA complexes will be examined in experiments determining the nature of RNA-protein and protein-protein interactions involved in the assembly of the icosahedral capsid. Morphological rearrangements occurring in the capsid during envelopment will be investigated. The development of functional capacities of virus membrane proteins (attachment and membrane fusion) will be examined.